I recently bought two 2GB sticks of OWC 800 MHz ram for my mac pro. My Mac Pro originally had two 1GB sticks, which worked fine, I just wanted more. It seems that they don't work together. I've tried every possibly configuration. Is it the case that they just aren't going to work together because they are different sizes? Right now, I have the two 2GB sticks in A1 and A2. And the stock 1GB sticks in B1 and B2. A1 and A2 gets detected, but B1 and B2 doesn't.